I don't think lockitron is truly NFC enabled. Their website talks about a NFC tag and an android phone. I could be wrong but I think they are using something like a NFC tasker to then activate the bluetooth on the phone to activate the lock. If this is the case, then the ring won't work on lockitron.

I thought I'd posted this here, but must have only commented on the kickstarter site - if you're having trouble finding NFC lock mechanisms another alternative would be to purchase some electric strike plates and a reader unit. It's possibly an easier installation and shouldn't alter the fire rating of your entry point as long as you re-seal any holes with retardant as you go. Both fail-open and fail-close versions are available and don't affect normal key based entry.

a) It would need to compete on pricing with Samsung units ~100$
b) It would need to be diverse enough to handle different type of door frames
c) It should support graceful fallback to a code unlock type
d) Code unlock should provide two random digits prior to the request of the code
e) It needs to notify a user of low battery
f) It needs to be mutable
g) It needs to be put into sleep mode and enabled on user interaction as to not constantly be looking for an NFC Device
h) It needs a simple UX for adding/remove NFC tags
i) It should retrofit over an existing Yale lock
j) It should be open source and fully documented so others can add to it / build on it.

Supporting international market demands and also persuading insurance companies they should provide pay outs should the door lock be exploited are other challenges..

At the moment the door lock / security situation most households face is dire and this is because insurance companies in the UK will only cover mortis and deadlock style locks, they basically say if someone can get in then not have to break out then you are uninsured.. A digital door lock always provides a single button exit (mostly for safety)..

Check out August.co, they are working on a BLE digital door lock, they are under the same VC as us but they don't seem very chatty, I don't know how they are getting on.. There are a few other BLE digital door locks and they aren't doing great, it's a really tough market because it's an incredibly old market.. Think about it, even Samsung haven't made a dent and their pockets are rediculously deep.. From what I can tell Samsung don't even really care about their digital door lock division, it's tiny...

Imho to launch an NFC door lock real world product would need ~1M funding and even then you aren't beginning to persuade people it's what they need.

Personally I can say it's for me the killer feature of the NFC Ring, the other stuff isn't anywhere near as practical.. Other people prefer using their ring to unlock their phone, it's each to their own but I use my ring on my door about 10 times a day and I love how simple it is and how I no longer have to worry about losing my keys..

So maybe an open source / community run digital door lock is a better solution, that way the development costs can be kept low.. It wont be as polished because it will have to use something like th ATMega328... You have to ask yourself though, do people really want to DIY their house door lock? It's a tough sell...

Me, I'll likely go the DIY route and as you mentioned use an atmega328. Purely because I love using atmegas in things though, the common reaction to me saying 'I will build my own door lock' tends to be first disbelief, then distaste, possibly at all the hassle involved. "But why do that when you can just go down to the hardware store and buy one."

If someone designed a relatively friendly version, cheap, that'd be a start.
Maybe they could then sort out some kind of bundle arrangement with the NFC ring team. The consumer loves the easy solution, couple that with a hefty dose of cool factor and a light sprinkling of 'oh hey we can use that on the phone too'.

If it happens sometime I'll support it and put my kludge away in the parts bin.

I will order parts first to build interface using Arduino and then create, if prototype looks promising a custom version with ATmega128. Will take some time, need to gather some money first, shouldn't be a big problem :) Problem is competition, I think johnny is right, this should be completely open source project so anyone could build it on it's own.

Those things would be nice, but easiest would just be NFC and leave an option to connect other things, arduino style controller would make this possible or perhaps use arduino compatible data lines. But the 'KISS' protocol is always the best one to follow in the first instance.

Me, I'll likely go the DIY route and as you mentioned use an atmega328. Purely because I love using atmegas in things though, the common reaction to me saying 'I will build my own door lock' tends to be first disbelief, then distaste, possibly at all the hassle involved. "But why do that when you can just go down to the hardware store and buy one."

The one I am designing uses electric strikes which are relatively cheap and allow you to keep the original hardware on the door (keys still work). I was planning on integrating with lockitron or something down the road to control the deadbolt. The reason for designing it like this is for something that doesn't require modification to your door or frame and still allows your original keys to work. The electric strikes won't fit in a wood doorframe without modification, but if you have a metal frame like my entryway, it should fit no problem. That is where I will be installing the first prototype.
I will upload a video of my breadboard solution shortly and edit this post.

That's excellent, strike plates are much easier to deal with in places where they require you to retain the fire rating for the door itself.
It's unfortunate that they tend to be so much bulkier than a standard plate, but it's the lesser of evils I reckon.

I have a strike lock on one of my inside doors, it performs relatively well but I dunno
a) What the power requirements are like compared to the conventional locks (not sure what they are called)? mortis maybe?
b) What insurance companies think about them.

What happens if power is removed from your system? Is the user still able to get out? I assume as there is some manual yale style handle on the inside that can be used?

You could almost fit a nano in the strike system btw, that'd be neat, then it's just an issue of providing power, my thought would be to use a smaller battery but use solar charging to keep it charged, not sure how feasible this is though!